MastocytosisOverview

Mastocytosis is a rare condition caused by an excess number of mast cells gathering in the body's tissues.

There are 2 main types of mastocytosis:

cutaneous mastocytosis, which mainly affects children – where mast cells gather in the skin, but are not found in large numbers elsewhere in the body

systemic mastocytosis, which mainly affects adults – where mast cells gather in body tissues, such as the skin, internal organs and bones

There are also several subtypes of systemic mastocytosis, depending on the symptoms.

Mast cells

Mast cells are produced in the bone marrow, the spongy tissue found in the hollow centres of some bones, and live longer than normal cells. They're an important part of the immune system and help fight infection.

When mast cells detect a substance that triggers an allergic reaction (an allergen), they release histamine and other chemicals into the bloodstream.

Histamine makes the blood vessels expand and the surrounding skin itchy and swollen. It can also create a build-up of mucus in the airways, which become narrower.

Symptoms of mastocytosis

The symptoms of mastocytosis can vary depending on the type.

Cutaneous mastocytosis

The most common symptom of cutaneous mastocytosis is abnormal growths (lesions) on the skin, such as bumps and spots, which can form on the body and sometimes blister.

Systemic mastocytosis

Some people with systemic mastocytosis may experience episodes of severe symptoms that last 15-30 minutes, often with specific triggers such as physical exertion or stress. Many people do not have any problems.